Vapor generators and superheaters



May 3, 1955 R. L. J. HAYDEN VAPOR GENERATORS AND SUPERHEATERS FiledMarch 27, 1951 nventors Clttorneg United States Patent O VAPOR GENERATRSAND SUPERHEATERS Application March 27, 1951, Serial No. 217,809 4Claims. (Cl. 1221) This invention relates to steam generators.ciiically, it is concerned with controlling the temperature in a steamgenerator.

In its most usual form, a vapor generator comprises a furnace red byburners and in which are arranged the steam generating tubes whichconnect the water drum to the steam drum. The saturated steam from thesteam drum passes to a superheater which is heated by furnace gaseswhich have already served for heating the steam generating tubes. Thosegases then proceed through a waste heat recovery system including aneconomizer and an air heater. The thus preheated air is used ascombustion air in the furnace.

In order to control the degree of superheat, i. e. the final steamtemperature, means may be provided for bypassing a certain proportion ofthe furnace gases round the superheater. This is not very satisfactory,however, in installations in which, at times, the degree of superheat isto be very low because, at those times, the residual heat in the furnacegases is greater than can be conveniently dealt with by the heatrecovery system.

An alternative manner of reducing the superheat is to provide atwo-stage superheater, i. e. a superheater having two sections connectedin series, and to cool or desuperheat the steam coming from the firstsection before feeding it to the second section. Generally, thedesuperheating medium is water which is thus preheated and serves asboiler feed water. It has, however, also been proposed to use air as adesuperheating medium and to use Vthe thus heated air as combustion air.Although air More spenal steam desuperheating has attractions, it hasthe disadvantage that where very low final steam temperatures arerequired, the air temperature becomes too high for the air to be used inthe furnace burners.

The present invention is concerned with the problem of enabling a watertube boiler to provide a wide range of superheat with a very lowminimum, otherwise than at the expense of the thermal economy of theboiler.`

According to the present invention, a water tube boiler is provided witha multi-stage superheater arranged to be heated by furnace gases whichhave served for the generation of steam, with a heat exchanger in whichsteam from an early superheating stageis cooled by indirect heatexchange with air before being passed to a later superheating stage andwith means for by-passing the furnace gases, when desired, round thesaid later superheating stage and with means for by-passing the airround the heat exchanger when desired.

ln the preferred form of boiler in accordance with the invention, acontroller is provided which is under the inuence of the inal steamtemperature and which automatically controls dampers regulating the owof the furnace gases through the superheater and also the flow of airthrough and round the heat exchanger.

The invention will be understood from the following description whenconsidered in connection with the accompanying drawing forming a partthereof, and in which 'ice the single figure is a diagrammatictransverse vertical section of the apparatus of the present invention.

Referring to the drawing, the apparatus of the present invention isdisclosed as embodied in a vapor generator comprising a setting 10having vapor generating surface therein with an upper steam and waterdrum 11 associated therewith together with a lower water drum 12 in thelower part of the setting in substantial vertical alignment with saidupper drum. Drums 11 `and 12 are connected by a substantially verticalbank of steam generating tubes 13.

At one side of the bank of tubes 13 is a furnace or combustion chamber14 fired, as shown, by a plurality of burners 15. The roof, side walland iioor of chamber 14 are lined by water tubes 16, 17 and 18.

At the side of the tube bank opposite to that on which the chamber 14 islocated is a substantially vertical extending gas passage 19 having anouter side wall 20 and an inner side Wall Ztl. Passage 19 has a4 lowergas inlet 21 at the bottom thereof and an intermediate gas inlet 22 inspaced relationship with said lower gas inlet. Lower gas inlet 21receives gases through a furnace gas outlet 23 controlled by a damper24, while intermediate gas inlet 22 of passage 19 receives gases througha furnace gas outlet 25 controlled by a damper 26. As shown, damper 24is in its open position so that gases passing over the tube bank 13 willflow into gas inlet 21 of gas passage 19, while damper 26 is illustratedas closed preventing the flow of gases into intermediate gas inlet 22.

A superheater having an upper or one section 27 with a saturated steaminlet 2S and a steam `outlet 29 is disposed in passage 19 aboveintermediate gas inlet 22. Upper section 27 receives steam from drum 11through saturated steam conduit 30 which communicates at the inlet endthereof with drum 11 and at the outlet end with saturated steam inlet 28of the upper superheater section. The superheater also has a lower orother section 31 having a desuperheated steam inlet 32 and 4a steamoutlet 33. Lower section 31 is disposed below intermediate gas inletpassage 22 and above gas inlet 2l.

As shown, gas passage 19 has economizer sections 34 and 3S positionedabove the superheater and also has an air heater 36 disposed thereinabove the economizer sections. The air heater comprises a plurality ofvertical tubular members 37 through which gases of combustion pass, saidair heater being divided into an upper pass 38 and a lower pass 39 by abattle 40. An air conduit 41 is disposed at the furnace chamber side ofsetting 10 and has a by-pass damper 42 therein which is disposedadjacent bafe 40. When damper 42 is closed, as illustrated, air iscaused to iiow through upper pass 38 of the air heater, through lowerpass 39 and thence back into duct 41. When the damper 42 is open, airflows directly through duct 41 by-passing the air heater. Duct t1communicates with a further duct 43 which has an enlarged portion 44 atthe upper part thereof and cornmunicates with burners 15 through anenlarged portion 45 at the bottom thereof.

The enlarged portion 44 of air duct 43 is divided into a verticallyextending by-pass passage 46 and a main passage 47 by a verticallyextending baffle 4d. By-pass passage 46 is controlled by a by-passdamper 49, while main passage 47 is controlled by a plurality of dampersSi?. As shown, by-pass damper 49 and dampers Sil are actuated by anactuator 51 through a lever S2, the dampers being so connected to lever52 that as by-pass damper 49 is actuated into a closed position, dampersStb are actuated into an opened position and as damper 49 is actuatedinto an opened position, dampers Si) are actuated into a closedposition. A tubular coil 53 forming a flow path for steam is positionedin main passage 47 below dampers 50, said coil having an inlet 54 and anoutlet 55. The

inlet 54 is in communication with steam outlet 29 of the uppersuperheater section 27 through steam conduit 56, while outlet 55 is incommunication with desuperheated steam inlet 32 through a conduit 57.

By-pass damper 4Z controlling the flow of air through air heater 36 isoperated by an actuator 53, while dampers 24 and 26 controlling the flowof gases into passage 19 through gas inlet passage 21 and intermediategas inlet passage 22 respectively are operated by an actuator 59.Actuators 51, 53 and 59 are operated by a damper controller 60 which isresponsive through thermostatic connection 61 to the outlet temperatureof steam flowing from lower section 31 of the superheater through steamoutlet 33.

When the vapor generator of the present invention is operating undernormal working conditions and a predetermined degree of superheat isrequired, damper controller 60 is set to the final temperature required.Dampers 24 and 26 are partially open so that gases flowing over tubebank 13 pass through furnace gas outlets 23 and 25 into passage 19through gas inlets 21 and 22 respectively, when said gases pass over thesuperheater sections thereafter to ow over economizer sections 34 and 35thence through tubular members 37 of air heater 36. By-pass damper 49and dampers Sti in air duct 43 are set as shown in the drawing, that is,these dampers are partially open so that a portion of the air passesover the tubular coil 53 and another portion flows through by-passpassage 46. Air heater by-pass damper 42 is in a partially closedposition so that a portion of the air will flow from duct 41 throughupper pass 38 of the air heater and thence through lower pass 39, whileanother portion of the air by-passes the air heater thereafter bothportions of the air flow into conduit 41 prior to passing into air duct43.

Should a higher final steam temperature be required, controller 60 isset to a higher temperature with the result that actuator 58 movesdamper 4 toward its closed position so that more air will ow through airheater 36, while actuator 51 will move by-pass damper 49 in conduit 43toward a more open position and at the same time moves dampers toward amore closed position so that less air flows over tubular coil 53.

Should a lower final temperature be required, controller is set to alower temperature thereby actuating actuator 58 so that damper 42 in airduct 41 is moved towards a more open position and a greater quantity ofair by-passes air heater 36 and actuates actuator 51 so that by-passdamper 49 is moved toward a closed position and dampers 50 are movedtoward an open position so that more air ows over tubular coil 53.Controller 60 will also control actuator 59 so that by-pass damper 24controlling the ow of gases over superheater section 31 is moved towarda closed position, while damper 26 controlling intermediate gas passage22 is moved toward an open position.

When the plant is idling and, therefore the degree of superheat is at aminimum, controller 60 is set at a minimum temperature with the resultthat damper 24 is entirely closed by actuator 59 and damper 26 isentirely open so that gases entirely by-pass superheater section 31.Damper 42 in air conduit 41 is completely open by actuator 58 so thatair by-passes air heater 36, while actuator 51 moves by-pass damper 49in airconduit 43 to a closed position and dampers 50 to a wide openposition so that all the air flows over coil 53 to the burners` vheating in the waste heat recovery system. f

Inasmuch as changes may be made in the form, loca-f. tion and relativearrangement of the several parts of the y apparatus disclosed Withoutdeparting from the essential characteristics of the invention, it willbe understood that the invention is not to be limited excepting by thescope of the appended claims.

What is claimed is:

1. In vapor generating apparatus comprising a vapor generator having asetting and means forming a saturated vapor space, a furnace in thesetting, said furnace having a gas outlet, means for firing the furnace,an air duct in communication with said furnace so as to conduct air tosupport combustion thereto, baffle means disposed in said duct so as todivide the duct longitudinally thereof into an air duct passage and anair duct by-pass passage laterally adjacent one another, air ductpassage damper means associated with said air duct passage, air ductby-pass passage damper means associated with said bypass passage,actuating means operatively associated with the damper means and theby-pass damper means so as to act simultaneously thereon to move saiddamper means and the by-pass damper means in directions opposite to oneanother, tubular means arranged to form a fluid path of ow and disposedin the air duct passage in heat exchange relationship with air flowingtherethrough, gas passage forming means having a passage gas inlet and agas outlet, the inlet being in communication with the furnace so as toreceive gases of combustion therefrom, a superheater disposed in saidgas passage forming means beyond the passage gas inlet in the directionof ow of the gases from the furnace and in heat exchange relationshipwith said gases, the superheater having a plurality of sections, onesection being positioned beyond and in spaced relationship with anothersection in respect to the flow of said gases through the passage, theportion of the gas passage forming means between the superheatersections being in communication with the furnace through an intermediategas inlet, the inlet of one of said superheater sections being incommunication with the saturated vapor space to receive vapor therefromand the outlet of said one superheater section being in communicationwith the vapor inlet of the tubular path of flow, the vapor inlet ofsaid other superheater section being in communication with the vaporoutlet of the tubular path of ow, a furnace gas damper disposed tocontrol the ow of gases from the furnace into said passage through theintermediate gas inlet, another furnace gas damper disposed to controlthe flow of gases from the furnace to said passage through said passagegas inlet, other actuating means operatively associated with the furnacegas damper and the other furnace gas damper so as to act simultaneouslyon said furnace gas damper and said other furnace gas damper to movesaid furnace gas damper toward a closed position when said other furnacegas damper is moved toward an opened position and vice versa, andcontrol means acting simultaneously on said actuating means and saidother actuating means and responsive to the temperature of superheatedvapor flowing from said other superheater section, said control meansbeing adapted to so operate the actuating means and other actuatingmeans when the temperature of the superheated vapor exceeds apredetermined degree as to cause the actuating means to move the airduct by-pass passage damper means toward a closed position wherein -ilowof air through the air duct by-pass passage is prevented and as to movetheair duct passage damper means toward an opened position wherein theflow of air through the air duct passage is permitted, and as to causethe other actuating means to move the furnace gas damper toward anopened position to permit flow of furnace gases through theintermediategas passage inlet and as to move the other furnace gas damper towardV aclosed position to prevent the flow of furnace gasesthrough the gaspassage inlet.

2. The apparatus of claim l wherein when the superlheated vaportemperature falls below a predetermined degree said control meanssimultaneously acts on said actuating means and said other actuatingmeans respectively to move the air duct by-pass damper means toward anopened position and the air duct damper means toward a closed position,and to move the furnace gas damper toward a closed position and theother furnace gas damper toward an opened position.

3. In vapor generating apparatus comprising a vapor generator having asetting and means forming a saturated Vapor space, a furnace in thesetting, said furnace having a gas outlet, means for firing the furnace,an air duct in communication with said furnace so as to conduct air tosupport combustion thereto, baffle means disposed in said duct so as todivide the duct longitudinally thereof into an air duct passage and anair duct by-pass passage laterally adjacent one another, air ductpassage damper means associated with said air duct passage, air ductby-pass passage damper means associated with said by-pass passage,actuating means operatively associated with the damper means and thebypass damper means so as to act simultaneously thereon to move saiddamper means and the by-pass damper means in directions opposite to oneanother, tubular means arranged to form a fluid path of flow anddisposed in the air duct passage in heat exchange relationship with airflowing therethrough, gas passage forming means having a passage gasinlet and a gas outlet, the inlet being in communication with thefurnace so as to receive gases of combustion therefrom, a superheaterdisposed in said gas passage forming means beyond the passage gas inletin the direction of flow of the gases from the furnace and in heatexchange relationship with said gases, the superheater having aplurality of sections, one section being positioned beyond and in spacedrelationship with another section in respect to the flow of said gasesthrough the passage, the portion of the gas passage forming meansbetween the superheater sections being in communication with the furnacethrough an intermediate gas inlet, the inlet of one of said superheatersections being in communication with the saturated vapor space toreceive vapor therefrom and the outlet of said one superheater sectionbeing in communication with the vapor inlet of the tubular path of ow,the vapor inlet of said other superheater section being in communicationwith the vapor outlet of the tubular path of flow, a furnace gas damperdisposed to control the ow of gases from the furnace into said passagethrough the intermediate gas inlet, another furnace gas damper disposedto control the flow of gases from the furnace to said passage throughsaid passage gas inlet, other actuating means operatively associatedwith the furnace gas damper and the other furnace gas damper so as toact simultaneously on said furnace gas damper and said other furnace gasdamper f to move said furnace gas damper toward a closed position whensaid other furnace gas damper is moved toward an opened position andvice versa, an air heater comprising heat exchange means wherein air andgases of combustion ow in indirect heat exchange relationship with oneanother, said heat exchange means communieating with said gas passagebeyond said one superheater section in the direction of flow of gasesthrough the passage to receive gases therefrom, the heat exchange meansbeing in communication with the air duct prior to said air duct passageand said air duct by-pass damper means in the direction of ow of air insaid duct, the air heater having an air flow by-pass passage thereinarranged to by-pass air around said heat exchange means, air flowby-pass damper means disposed to control the flow of air through saidair ow by-pass passage, further actuating means operatively associatedwith the air ow by-pass damper means to actuate said air flow by-passdamper means, and control means acting on said actuating means, saidother actuating means and said further actuating means, said controlmeans being responsive to the ternperature of superheated vapor flowingfrom said other superheater section, said control means being adapted toso operate the actuating means, other actuating means, and furtheractuating means when the temperature of the superheated vapor exceeds apredetermined degree as to cause the actuating means to move the airduct byapass passage damper means toward a closed position wherein Howof air through the air duct by-pass passage is prevented and as to movethe air duct passage damper means toward an opened position wherein owof air through the air duct passage is permitted, and as to cause theother actuating means to move the furnace gas damper toward an openedposition to permit ow of furnace gases through the intermediate gaspassage inlet and as to move the other furnace gas damper toward aclosed position to prevent the flow of furnace gases through the gaspassage inlet, and as to cause the air flow bypass damper means to movetoward an opened position wherein flow of air through the air flowby-pass passage is permitted.

4. The apparatus of claim 3 wherein when the superheated vaportemperature falls below a predetermined degree said control meanssimultaneously acts on said actuating means, the other actuating meansand said further actuating means respectively to move the air ductby-pass damper means toward an opened position and the air duct dampermeans toward a closed position, to move the furnace gas damper toward aclosed position and the other furnace gas damper toward an openedposition, and to move said air flow by-pass damper means toward itsclosed position.

References Cited in the file of this patent UNITED STATES PATENTS1,785,334 Black Dec. 16, 1930 1,983,624 Lundgren Dec. 1l, 1934 FOREIGNPATENTS 575,509 Great Britain Feb. 21, 1946

1. IN VAPOR GENERATING APPARATUS COMPRISING A VAPOR GENERATOR HAVING ASETTING AND MEANS FORMING A SATURATED VAPOR SPACE, A FURNACE IN THESETTING, SAID FURNACE HAVING A GAS OUTLET, MEANS FOR FIRING THE FURNACE,AN AIR DUCT IN COMMUNICATION WITH SAID FURNACE SO AS TO CONDUCT AIR TOSUPPORT COMBUSTION THERETO, BAFFLE MEANS DISPOSED IN SAID DUCT SO AS TODIVIDE THE DUCT LONGITUDINALLY THEREOF INTO AN AIR DUCT PASSAGE AND ANAIR DUCT BY-PASS PASSAGE LATERALLY ADJACENT ONE ANOTHER, AIR DUCTPASSAGE DAMPER MEANS ASSOCIATED WITH SAID AIR DUCT PASSAGE, AIR DUCTBY-PASS PASSAGE DAMPER MEANS ASSOCIATED WITH SAID BYPASS PASSAGE,ACTUATING MEANS OPERATIVELY ASSOCIATED WITH THE DAMPER MEANS AND THEBY-PASS DAMPER MEANS SO AS TO ACT SIMULTANEOUSLY THEREON TO MOVE SAIDDAMPER MEANS AND THE BY-PASS DAMPER MEANS IN DIRECTIONS OPPOSITE TO ONEANOTHER, TUBULAR MEANS ARRANGED TO FORM A FLUID PATH OF FLOW ANDDISPOSED IN THE AIR DUCT PASSAGE IN HEAT EXCHANGE RELATIONSHIP WITH AIRFLOWING THERETHROUGH, GAS PASSAGE FORMING MEANS HAVING A PASSAGE GASINLET AND A GAS OUTLET, THE INLET BEING IN COMMUNICATION WITH THEFURNACE SO AS TO RECEIVE GASES OF COMBUSTION THEREFROM, A SUPERHEATERDISPOSED IN SAID GAS PASSAGE FORMING MEANS BEYOND THE PASSAGE GAS INLETIN THE DIRECTION FLOW OF THE GASES FROM THE FURNACE AND IN HEAT EXCHANGERELATIONSHIP WITH SAID GASES, THE SUPERHEATER HAVING A PLURALITY OFSECTIONS, ONE SECTION BEING POSITIONED BEYOND AND IN SPACED RELATIONSHIPWITH ANOTHER SECTION IN RESPECT TO THE FLOW OF SAID GASES THROUGH THEPASSAGE, THE PORTION OF THE GAS PASSAGE FORMING MEANS BETWEEN THESUPERHEATER SECTIONS BEING IN COMMUNICATION WITH THE FURNACE THROUGH ANINTERMEDIATE GAS INLET, THE INLET OF ONE OF SAID SUPERHEATER SECTIONSBEING IN COMMUNICATION WITH THE SATURATED VAPOR SPACE TO RECEIVE VAPORTHEREFROM AND THE OUTLET OF SAID ONE SUPERHEATER SECTION BEING INCOMMUNICATION WITH THE VAPOR INLET OF THE TUBULAR PATH OF FLOW, THEVAPOR INLET OF SAID OTHER SUPERHEATER SECTION BEING IN COMMUNICATIONWITH THE VAPOR OUTLET OF THE TUBULAR PATH OF FLOW, A FURNACE GAS DAMPERDISPOSED TO CONTROL THE FLOW OF GASES FROM THE FURNACE INTO SAID PASSAGETHROUGH THE INTERMEDIATE GAS INLET, ANOTHER FURNACE GAS DAMPER DISPOSEDTO CONTROL THE FLOW OF GASES FROM THE FURNACE TO SAID PASSAGE THROUGHSAID PASSAGE GAS INLET, OTHER ACTUATING MEANS OPERATIVELY ASSOCIATEDWITH THE FURNACE GAS DAMPER AND THE OTHER FURNACE GAS DAMPER SO AS TOACT SIMULTANEOUSLY ON SAID FURNACE GAS DAMPER AND SAID OTHER FURNACE GASDAMPER TO MOVE SAID FURNACE GAS DAMPER TOWARD A CLOSED POSITION WHENSAID OTHER FURNACE GAS DAMPER IS MOVED TOWARD AN OPENED POSITION ANDVICE VERSA, AND CONTROL MEANS ACTING SIMULTANEOUSLY ON SAID ACTUATINGMEANS AND SAID OTHER ACTUATING MEANS AND RESPONSIVE TO THE TEMPERATUREOF SUPERHEATED VAPOR FLOWING FROM SAID OTHER SUPERHEATER SECTION, SAIDCONTROL MEANS BEING ADAPTED TO SO OPERATE THE ACTUATING MEANS AND OTHERACTUATING MEANS WHEN THE TEMPERATURE OF THE SUPERHEATED VAPOR EXCEEDS APREDETER MINED DEGREE AS TO CAUSE THE ACTUATING MEANS TO MOVE THE AIRDUCT BY-PASS PASSAGE DAMPER MEANS TOWARD A CLOSED POSITION WHEREIN FLOWOF AIR THROUGH THE AIR DUCT BY-PASS PASSAGE IS PREVENTED AND AS TO MOVETHE AIR DUCT PASSAGE DAMPER MEANS TOWARD AN OPENED POSITION WHEREIN THEFLOW OF AIR THROUGH THE AIR DUCT PASSAGE IS PERMITTED, AND AS TO CAUSETHE OTHER ACTUATING MEANS TO MOVE THE FURNACE GAS DAMPER TOWARD ANOPENED POSITION TO PERMIT FLOW OF FURNACE GASES THROUGH THE INTERMEDIATEGAS PAS SAGE INLET AND AS TO MOVE THE OTHER FURNACE GAS DAMPER TOWARD ACLOSED POSITION TO PREVENT THE FLOW OF FURNACE GASES THROUGH THE GASPASSAGE INLET.